Hitachi Industrial Equipment Systems Co., Ltd.

Kazushige Hotta

Yusuke Arao

Hiroshi Watanabe

Hiroyuki Tomita

Masahiro Hiraga

Yusaku Onuma

Atsuhiko Nakamura

Naoki Takata

Keisuke Tanabe

Masataka Sasaki

The purpose of the present invention is to provide a speed detection method for maintaining a fine time axis resolution and a power conversion device that uses the method. This power conversion device comprises an inverter for converting DC voltage into AC voltage and supplying the same to a motor, a motor speed calculation unit for calculating the speed of the motor from output pulses obtained from an encoder connected to the motor, and a control unit for receiving the motor speed from the motor speed calculation unit and controlling the inverter. In the power conversion device, the motor speed calculation unit measures the duty cycle of the output pulses, calculates the speed using the half cycles of the output pulses if the duty cycle is within a prescribed range from 50%, and calculates the speed using the full cycles of the output pulses if the duty ratio is outside of the prescribed range from 50%.

Speed calculation device and power conversion device

This voltage imbalance assessment method is for a power conversion device comprising a forward converter for rectifying the voltage of a three-phase AC power supply, a smoothing capacitor for smoothing the rectified voltage, a detection unit for detecting the smoothed voltage, and a control unit. The control unit: uses the detected voltage to generate data indicating frequency components; compares, in the data indicating frequency components, the magnitude of the component that is four times the power supply frequency with the magnitude of the component that is six times the power supply frequency; and assesses the voltage imbalance of the three-phase AC power supply on the basis of the comparison.

Voltage imbalance assessment method and power conversion device

Provided is a power conversion device with which it is possible to acquire a sign of a system stop before the system stops, and to minimize the nonworking time of the system. A power conversion device for converting DC voltage or AC voltage into AC voltage, the power conversion device being characterized by having an abnormality detection unit for detecting abnormalities in the power conversion device, a restart unit for stopping the power conversion device and automatically performing a restart when the abnormality detection unit has detected an abnormality, a restart recording unit for recording restart information of when the restart unit has restarted, and a sign diagnostic unit for inputting the restart information recorded by the restart recording unit and performing a sign diagnosis of the abnormality in the power conversion device on the basis of the restart information, the sign diagnostic unit performing the sign diagnosis on the basis of the number of restarts and outputting a sign diagnostic result.

Power conversion device and power conversion device system

Growing community of inventors

Tokyo, Japan

Kazushige Hotta